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FreeBSD-SA-05:16.zlib                                       Security Advisory
                                                          The FreeBSD Project

Topic:          Buffer overflow in zlib

Category:       core
Module:         libz
Announced:      2005-07-06
Credits:        Tavis Ormandy
Affects:        FreeBSD 5.3, FreeBSD 5.4
Corrected:      2005-07-06 14:01:11 UTC (RELENG_5, 5.4-STABLE)
                2005-07-06 14:01:30 UTC (RELENG_5_4, 5.4-RELEASE-p4)
                2005-07-06 14:01:52 UTC (RELENG_5_3, 5.3-RELEASE-p18)
CVE Name:       CAN-2005-2096

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

zlib is a compression library used by numerous applications to provide
data compression/decompression routines.

II.  Problem Description

An error in the handling of corrupt compressed data streams can result
in a buffer being overflowed.

III. Impact

By carefully crafting a corrupt compressed data stream, an attacker can
overwrite data structures in a zlib-using application.  This may cause
the application to halt, causing a denial of service; or it may result
in the attacker gaining elevated privileges.

IV.  Workaround

No workaround is available.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE, or to the RELENG_5_4 or
RELENG_5_3 security branch dated after the correction date.

2) To patch your present system:

The following patch has been verified to apply to FreeBSD 5.3 and 5.4
systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:16/zlib.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:16/zlib.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libz/
# make obj && make depend && make && make install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_5
  src/lib/libz/inftrees.c                                         1.4.2.2
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.13
  src/sys/conf/newvers.sh                                   1.62.2.18.2.9
  src/lib/libz/inftrees.c                                         1.4.6.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.21
  src/sys/conf/newvers.sh                                  1.62.2.15.2.23
  src/lib/libz/inftrees.c                                         1.4.4.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-2096

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:16.zlib.asc
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